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Discussion Starter #1
I have a 2008 Exige S240 with no engine mods.
I've been logging IAT through OBD2 port via Torque Pro app for some time, and I've noticed that it gets unreasonably(?) high by the end of the session.

I have a few hypotheses:
1. Stock intercooler is getting heat soaked.
2. IAT is being overrun by blow-by vapor and is reading higher than the actual value.
3. All system is normal, the IAT sensor is just reading wrong.
4. Torque App is wrong.

My guess is either 1 or 2, because the IAT usually starts off at ambient temperature and starts climbing up, as well as losing up to 10degC when I'm not on throttle in the corners after the straightaways.
2 is a possible suspect if I get more than a few drips of oil inside when I take the intercooler off for cleaning and inspection.

So, the question becomes, what kind of IAT is considered 'acceptable'?
What strategy does the car employ when it sees high IAT? (pulling timing after certain temperature threshold?)
Is the maximum figure relative to ambient temperature? (ex: 80degC IAT at 20degC/68F ambient is bad but, 95degC IAT at 46degC/115F is acceptable???)

How high of IAT have you all seen in your car, and how did you combat it? Any before/after figures?

I'll either be getting a 3 chamber shroud or just upgrade to proalloy or RLS intercooler in the future, but I'd like to hear some thoughts on this.
 

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Put a catch can on the car and see if that has any effect.
Clean the oil out of the IC pipes and silicone connectors.
Wrap some heat reflective tape on the right side IC horseshoe pipe.

I've done all three but don't data log. Does you S240 lack high end power? Mine has great low end torque but anything past 100 mph and it seems to hit a wall....meaning the rate of acceleration decreases considerably and the engine seems to just make a nice noise. Car has 9000 miles.


If you look at the IC core you'll be aghast at the amount of oil
coating the IC fins on a care without a catch can.
I started a thread about ways to clean the inside of IC, but haven't gotten any answers yet.
 

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The stock ECU for certain pulls timing with increasing IAT's. It might also enrich the mixture during open loop (mid throttle or more), but I don't know if the stock programming does that or not. The advantage of enriching the mixture is that vaporization of the extra fuel gives a cooling effect, but it also hurts emissions and mpg, so my guess is that the stock ECU only pulls timing with increasing IAT's.

So the good news is that the engine doesn't self destruct from knock with high IAT's, but you do lose power and the exhaust gas temperatures can go quite high (retarding the timing increases EGT's at WOT). Cleaning the I/C, a larger and more efficient I/C, and most importantly adding air flow ("fettle" the roof intake, a 3 shroud intake, and/or puller fans on the I/C) will all help reduce heat soak.

HTH,
 

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I think your data is just confirming what one would expect from the IC setup.

There is only a few in sq of intake area and its right in the boundary layer of the room. Designed by a lotus intern no doubt.

Best solution would be to get more air to the stock IC. I have my doubts about weather a larger core is very helpful. The stock core looks fine for 250+ HP, if you can get it reasonable air flow.
 

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roof not room. I are not gooder at typing
 

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IAT's are always going to be higher than ambient on passively-cooled forced induction cars. How high is too much usually depends on the tuners opinion. I've seen IAT's past 300°F on certain cars [poorly intercooler highly overdriven supercharged setups].

ECU's with IAT feedback usually retard spark and/or add fuel with elevated IAT's for that specific setup. The intent is to reduce knock; of course using the knock sensor in that equation helps the ECU get maximum power while still remaining safe considering the situation. I just realized I pretty much echo'd AustinP's comments before I even read them. LOL

The Exige S is fairly notorious for having poor IC airflow on top of the stock IC have low thermal inertia, resulting in the IC setup "heatsoaking" after as soon as the warm-up lap. Going with a full-on RLS setup [bigger IC plus chambered shroud using side scoops for additional airflow] is a great solution for the track.
 

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You'll have to define what "tolerable" means. If that means what will the engine handle before melting down, then you need not worry. You'll never get IAT hotter than combustion.

If it's hotter than what the tune can safely compensate for, then again, you need not worry because the stock ECU has plenty of IAT spark retard built in.

So that really only leaves power to question. All the FI systems "heat soak", some just heat soak at a higher level than others. You cannot really get a good idea of what your system's true heat soaked operating point/temp is unless on the track. Think of heat soak more of the equilibrium of your IC's actual operating efficiency relative to ambient air temps. On a 100 degree day, the Exige S blower, pre IC, puts out about 260 degree air and the stock IC will run about 210 degrees air into the motor on the track where duty cycle is as close to 100% as a motor will see. That's "tolerable" at the motor level but will have a significant impact on power. At that IAT, air density is lower and spark advance has been retarded to the point where power will be well under 200whp. So the question is less about whether that IAT is tolerable and more to the point of whether that power level is tolerable...

If you're recording your times or are competing, etc, then the power level that is derived from that IAT may not be acceptable/tolerable.

-Phil
 

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...
Wrap some heat reflective tape on the right side IC horseshoe pipe.
...
If the AIT is higher then the water temp, that will at least keep the engine from getting warmer from the heat radiated from the IC.



I have a 2008 Exige S240 with no engine mods.
...

I have a few hypotheses:
1.
2.
3. All system is normal, the IAT sensor is just reading wrong.
4.
...
It is common to disbelieve the gauges. Usually a fatal mistake when pilots do that.
 

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Discussion Starter #11
Put a catch can on the car and see if that has any effect.
Clean the oil out of the IC pipes and silicone connectors.
Wrap some heat reflective tape on the right side IC horseshoe pipe.

I've done all three but don't data log. Does you S240 lack high end power? Mine has great low end torque but anything past 100 mph and it seems to hit a wall....meaning the rate of acceleration decreases considerably and the engine seems to just make a nice noise. Car has 9000 miles.


If you look at the IC core you'll be aghast at the amount of oil
coating the IC fins on a care without a catch can.
I started a thread about ways to clean the inside of IC, but haven't gotten any answers yet.
Yes, this has been worrying me since Summer is here and the temperature will be 100+F real soon.
I'm evaluating which catch cans would best fit my needs(Function > OEM Look > Cost > Ease of Maintenance). The choices are pretty limited from the Lotus specific vendors, and I think I might find better engineered solution from 3rd party vendors. The worst is no one ever does the effectiveness comparison tests.

I don't usually take the car upto 100+mph anywhere, and it's hard to tell because I only get that high of IAT only in track day conditions, and the tracks I go to run out of straights before I hit 5th(115mph+mph).
The car still pulls ok, although I can hit 5th usually in the mornings or beginnging of the sessions but not later in the day. Looking at data tells me upshifting to 5th just for 1~2seconds is worse than staying in 4th, though.
The Exige has fairly large coefficient of drag at 0.43, and it becomes relavent especially at higher speeds(drag becomes squared vs speed). I do recall feeling like I've hit the aero wall around 120+mph.

Putting reflective films on the pipe is an interesting idea, I'll look into it. But I think it might be good for chasing the last few degrees, although ever little bit helps.

I did take apart the intercooler and the hoses prior to my recent track day for the first time in 18k miles, but fortunately I only found maybe a teaspoon of oil in the intercooler.
I poured half a cup of acetone inside the intercooler and gave it a good shake to get all the crap out and the result was ok. Just make sure not to get any on the outside as the intercooler is actually PAINTED, NOT ANODIZED. I did a little test dab in the corner before proceeding, and tiny bit of paint does come off.
 

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Discussion Starter #12
The stock ECU for certain pulls timing with increasing IAT's. It might also enrich the mixture during open loop (mid throttle or more), but I don't know if the stock programming does that or not. The advantage of enriching the mixture is that vaporization of the extra fuel gives a cooling effect, but it also hurts emissions and mpg, so my guess is that the stock ECU only pulls timing with increasing IAT's.

So the good news is that the engine doesn't self destruct from knock with high IAT's, but you do lose power and the exhaust gas temperatures can go quite high (retarding the timing increases EGT's at WOT). Cleaning the I/C, a larger and more efficient I/C, and most importantly adding air flow ("fettle" the roof intake, a 3 shroud intake, and/or puller fans on the I/C) will all help reduce heat soak.

HTH,

I do remember hearing about how the engine starts pulling timing above 70degC, but I haven't found evidence for that particular number so I'm considering it a useful hearsay.
Timing advance has gotten logged(not all the time), but I haven't seen it change that much at high IAT. Maybe that's due to the fact that the car was already heat soaked or I have no idea wtf I am looking at(not improbable).
I might start logging EGT, but I don't believe it's at worrying level especially at stock configuration.
 

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Discussion Starter #13
I think your data is just confirming what one would expect from the IC setup.

There is only a few in sq of intake area and its right in the boundary layer of the room. Designed by a lotus intern no doubt.

Best solution would be to get more air to the stock IC. I have my doubts about weather a larger core is very helpful. The stock core looks fine for 250+ HP, if you can get it reasonable air flow.
Yeah, I think the intake should go higher and out of the boundary layer. I'd imagine it was probably styling driven at worst and drag driven at best.
Interesting thing is that Adrian Newey's Exige more or less kept the the intake portion of the roof scoop, but of course, the entire tunnel has been enlaged substancially...

 

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Discussion Starter #14
IAT's are always going to be higher than ambient on passively-cooled forced induction cars. How high is too much usually depends on the tuners opinion. I've seen IAT's past 300°F on certain cars [poorly intercooler highly overdriven supercharged setups].

ECU's with IAT feedback usually retard spark and/or add fuel with elevated IAT's for that specific setup. The intent is to reduce knock; of course using the knock sensor in that equation helps the ECU get maximum power while still remaining safe considering the situation. I just realized I pretty much echo'd AustinP's comments before I even read them. LOL

The Exige S is fairly notorious for having poor IC airflow on top of the stock IC have low thermal inertia, resulting in the IC setup "heatsoaking" after as soon as the warm-up lap. Going with a full-on RLS setup [bigger IC plus chambered shroud using side scoops for additional airflow] is a great solution for the track.
Thanks, it still helps.
I was just trying to put my finger on upper limit of what IAT would be like.
The 3 chamber shroud set up is what I'm ultimately looking into, but the RLS setup is unattractively priced for me.
I might end up creating something similiar with stock shroud or with sheet aluminum or something.
 

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Discussion Starter #15
You'll have to define what "tolerable" means. If that means what will the engine handle before melting down, then you need not worry. You'll never get IAT hotter than combustion.

If it's hotter than what the tune can safely compensate for, then again, you need not worry because the stock ECU has plenty of IAT spark retard built in.

So that really only leaves power to question. All the FI systems "heat soak", some just heat soak at a higher level than others. You cannot really get a good idea of what your system's true heat soaked operating point/temp is unless on the track. Think of heat soak more of the equilibrium of your IC's actual operating efficiency relative to ambient air temps. On a 100 degree day, the Exige S blower, pre IC, puts out about 260 degree air and the stock IC will run about 210 degrees air into the motor on the track where duty cycle is as close to 100% as a motor will see. That's "tolerable" at the motor level but will have a significant impact on power. At that IAT, air density is lower and spark advance has been retarded to the point where power will be well under 200whp. So the question is less about whether that IAT is tolerable and more to the point of whether that power level is tolerable...

If you're recording your times or are competing, etc, then the power level that is derived from that IAT may not be acceptable/tolerable.

-Phil
That's a relief! I was worried about potential knock/detonation due to high IAT.
I chose my word carefully in hopes of discovering what IAT individuals found acceptable.

My car is mostly driven on track, and your figures of 260/210F more or less represents what I'm getting.
Here is me hitting 203F at the end of the straight in 90F ambient.

Now that my question has been fully answered by many of the folks here, my new question would be finding a reasonable IAT level I should aim for. I guess a temperature level where the engine doesn't pull too much timing and adversely affect performance.
Of course lower the IAT the better, and I could even run iceboxed intercooler like some of the drag racing people do, but let's be reasonable and realistic here.
 

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...I might start logging EGT, but I don't believe it's at worrying level especially at stock configuration.

There is no stock EGT sensor, you'd have to add a probe to the exhaust manifold and a data logger. But I wouldn't bother unless you are doing your own tuning. Given the number of reports of fried cats and muffler packing on tracked SC'd Exiges, I'm thinking the exhaust gas temps do, in fact, get pretty toasty under full boil. Cooler intake temps, and thus less timing retard, will help (of course also helps with hp).





Sent from AutoGuide.com Free App
 

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That's a relief! I was worried about potential knock/detonation due to high IAT.
I chose my word carefully in hopes of discovering what IAT individuals found acceptable.

My car is mostly driven on track, and your figures of 260/210F more or less represents what I'm getting.
Here is me hitting 203F at the end of the straight in 90F ambient.
2014 June Thunderhill 5mi with GGLC - clean lap - YouTube

Now that my question has been fully answered by many of the folks here, my new question would be finding a reasonable IAT level I should aim for. I guess a temperature level where the engine doesn't pull too much timing and adversely affect performance.
Of course lower the IAT the better, and I could even run iceboxed intercooler like some of the drag racing people do, but let's be reasonable and realistic here.

What do you mean by "reasonable IAT level I should aim for"? I suppose it's all reasonable. The lower the IAT, the more potential power.

The Lotus tunes pull 6, yes 6 degrees of spark advance at 158F. Heck, they pull 1 degree at 104F! It makes no sense. With all the RLS goodies you can find, you could get the IATs down to 160-170F of your 90 degree day on the track with stock boost. So that's a great comparatively, but you'll still be at max spark retard for a Lotus calibration. The KF, VF/CX, and Sector tunes all have the same IAT retard tables. The only tunes on the stock ECU that change those tables are our Torque tunes, but we don't have them for black dash cars yet.

If you put a smaller pulley on there, the IATs will climb but the manifold pressure will too...

So here's what the math says and it's pretty much accurate with what the dyno shows...

1) With your current setup, assuming best spark (which you don't have with -6 IAT compensations) you'd make about 195whp. That's with 90F ambient, 3 psi pressure drop, stock boost, and ~40% efficient

2) If you go the RLS stuff, shrouds, etc, and get temps down to 165F, you'd gain some pressure, as they have maybe 1 psi less pressure drop, and 60% efficient IC. So all else equal to above, you might make as much as 217whp....again, assuming best timing...

Assuming the tune is a constant, you can probably assume that adding airflow and the RLS IC might be worth approx 22whp from on an otherwise stock setup on the track... aka: real world

3) if you pulley down to a 3" pulley and pick up another 2.5psi boost, the IATs will probably climb to 180F, but power could bump up to 232whp at heat soak... So that's another 15whp... again, those deltas are about what the dyno shows (albeit dyno is relatively higher numbers everywhere since it's not quite as hot on the dyno as track)... You won't get those power levels on the stock or currently available aftermarket tunes because the IAT compensations are wrong, but you probably get the idea...

-Phil
 

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Thanks, it still helps.
I was just trying to put my finger on upper limit of what IAT would be like.
The 3 chamber shroud set up is what I'm ultimately looking into, but the RLS setup is unattractively priced for me.
I might end up creating something similiar with stock shroud or with sheet aluminum or something.
As long as you AIT is temp is higher than the engine temp then insulating the air with a shroud will probably not help a whole lot.
It could could help if there was exhaust radiating onto the intake, but there is little evidence that those shrouds do a whole lot... But they do look nice.
 

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^^furthermore there isn't a lot of surface area in contact with the charge for very long while it's just in a transport tube, so the insulation can't do too much.... but then again, every little bit sort of thing....
 

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